The present invention relates to hot water dispensers with an integral heating element in which water is maintained at a useful temperature in a location proximate the dispensing outlet. The dispenser is provided with a main chamber and an expansion chamber. As the cold water is heated, some water expands into an expansion chamber through the inlet pipe and inlet pipe aspirator hole. When the dispenser is dispensing, cold water passing through an inlet pipe and venturi aspirates hot water from the expansion chamber and through the aspirator hole and mixes it with the incoming cold water. The incoming cold water displaces the hot water in the main chamber through an outlet pipe connected to the dispenser or faucet outlet. The expansion chamber prevents expanded water from dripping out the faucet spout during the heating cycle. U.S. Pat. No. 3,891,124 is illustrative of an aspirator in the cold water inlet side of the system.
The water tank of the present invention includes an upper tank section molded from plastic and a lower metallic or brass section. It is known to have water tanks with upper plastic sections and lower metallic sections. U.S. Pat. No. 3,730,144 discloses a hot liquid dispenser which has a transparent plastic upper tank section to enable inspection of the interior. In the present invention, the plastic upper tank section has integrally molded therein various of the plumbing connection components. In addition, the plastic tank section comprises the major portion of the tank and the insulating capabilities of the plastic tank reduce energy consumption.
For safety reasons, most instant hot water dispensers operate at atmospheric pressure and have an air vent passage for the tank which terminates in a protected enclosure such as the dispensing valve to insure that the air vent is not obstructed, which could cause a pressure build-up.